The Messenger of Allah ﷺ said, "How remarkable is the affair of the believer! All of his affairs are good, and this is not the case for anyone except the believer. If something pleasing befalls him, he gives thanks, and that is good for him. If something harmful befalls him, he endures it patiently, and that is good for him."
قال رسول الله ﷺ: عجبا لأمر المؤمن، إن أمره كله خير، وليس ذاك لأحد إلا للمؤمن، إن أصابته سراء شكر فكان خيرا له، وإن أصابته ضراء صبر فكان خيرا له.
Muslim narrated it in Zuhd (2999) from Haddab bin Khalid Azdi and Shayban bin Faruq, both from Sulayman bin Mughira. He said, Sulayman narrated to us, Thabit narrated to us, from Abdul-Rahman bin Abu Layla, from Suhayb, and he mentioned it.Bayhaqi (3/375) narrated it by way of Ahmad bin Nadr bin Abdul-Wahhab, from Shayban bin Faruq with the same wording, and he added at the end, "So every decree of Allah for the Muslims is good."